Catalyst for the selective decomposition of cumene hydroperoxide and process using it

ABSTRACT

The invention relates to a catalyst for the selective decomposition of cumene hydroperoxide, constituted by zeolite crystals wherein a portion of the silicon atoms in thecrystal lattice of silica is replaced by Al and B, the seolite crystals being bonded to each other by a siliceous bonding agent which allows the catalyst to assume the shape of mechanically stable microspheres. 
&lt;??&gt;The invention relates also to the process in which the catalyst is used, and to the related operating conditions.

This application is a divisional of application Ser. No. 854,527, filedon Apr. 22, 1986, and now U.S. Pat. No. 4,743,573.

The present invention relates to a catalyst for the selectivedecomposition of cumene hydroperoxide and to a process using thiscatalyst.

In the synthesis of phenol and acetone, one of the methods used on anindustrial scale is the synthesis of cumene from benzene and propylene,a subsequent peroxidation to cumene hydroperoxide, and an acid-catalyzeddecomposition of the peroxide into phenol and acetone.

The decomposition of cumene hydroperoxide is generally carried out inthe presence of H₂ SO₄. This process leads to the formation of a mixturecomposed of: phenol, acetone, acetophenone and sulphonated byproducts,the separation of which has a considerable effect on the productioncosts and on the complexity of the plant. It has now been surprisinglyfound that such a decomposition can be carried out with a higherconversion and selectivity to phenol and acetone, and without thedrawbacks involved by the separation of H₂ SO₄ and of its derivatives,by using a catalyst composed of zeolite crystals, wherein a portion ofthe silicon atoms of the crystal lattice of silica is replaced by Al andB. The zeolite crystals are bonded to each other by means of a siliceousbonding agent, which allows the catalyst to assume the shape ofmechanically stable microspheres.

A first object of the present invention is to provide a catalyst for theselective decomposition of cumene hydroperoxide into phenol and acetoneon the basis of silicon, aluminium and boron, wherein silicon, aluminiumand boron, in the form of their oxides, constitute crystals having astructure of the zeolite type, wherein aluminium and boron replacesilicon in the crystalline structure of silica, and the crystals areinterconnected with each other by oligomeric silica.

The molar ratio between the silica of zeolite crystals and theoligomeric silica is within the range of from 80 to 95.

The catalyst according to the present invention is in the form ofmicrospheres having dimensions ranging from 5 μm to 1000 μm, preferablyfrom 20 μm to 100 μm.

The catalyst according to the present invention has the followinggeneral formula (after calcination at 550° C. and cooling to roomtemperature): 0.017-0.0025 Al₂ O₃.0.1-0.005 B₂ O₃.SiO₂.0.2-0.5 H₂ O.

A second object of the present invention is to provide a method for thepreparation of the above catalyst.

The catalyst is prepared by a two-step process, the first step of whichis the preparation of the above zeolite crystals and the second of whichis the interconnecting of the above zeolite crystals, by compounds ableto form oligomeric silica.

The first step is accomplished by starting from alkyl silicates (alkylgroups of from 1 to 4 carbon atoms), in particular from tetramethyl-and/or tetraethylsilicate, possibly in aqueous solution, which are addedto an alcoholic solution (aliphatic alcohol of from 1 to 6 carbon atoms)of an aluminium salt at a concentration of preferably from 4 to 5%,preferably an alcoholic solution of Al nitrate or acetate. The wholesolution then is mixed with an aqueous solution of tetrapropylammoniumhydroxide and H₃ BO. From the reaction medium foreign cations, inparticular cations of alkaline or alkaline-earth metals, must be absent.

The whole solution is heated under stirring to a temperature within therange of from 50° to 80° C., preferably to 60° C., for the purpose ofhydrolyzing the alkyl silicate and removing an amount as high aspossible of the alkyl alcohol obtained from the hydrolysis and of thealcohol coming from the solution of the aluminium salt.

After the hydrolysis of the alkyl silicate and the removal of alcohols,the resulting residual solution is charged into an autoclave equippedwith a stirrer, and is heated, under its autogenous pressure, at atemperature of from 150° to 250° C., for a time period of from 3 hoursto 10 days. A suspension of crystals is obtained. The crystals of thesuspension are then separated from the the mother liquids, preferably bycentrifuging, washed in deionized water and dried, preferably bycentrifuging.

The second step consists in dispersing the above zeolite crystals in aclear solution obtained by hydrolyzing a tetraalkyl silicate (alkylgroup of from 1 to 4 carbon atoms), preferably tetramethyl- ortetraethyl-silicate, in an aqueous solution of tetraalkylammonium (TAA)hydroxide (alkyl group of from 1 to 5 carbon atoms) for a time of from 1to 2 hours at a temperature of 60°-70° C.

The suspension obtained is atomized, preferably by means of a spraydrier, and microspheres having an average diameter of from 5 to 1000 μm,preferably of from 20 to 100 μm, are obtained.

The microspheres are then calcined at a temperature of from 500° to 600°C., preferably at 550° C. for 2-10 hours, preferably for 5 hours.

The reaction mixture for the synthesis of the zeolite has the followingmolar composition: 0.1-0.35 (TPA₂)O; SiO₂ ; 0.0025-0.01 Al₂ O₃ ;0.2-0.02 B₂ O₃ ; 20-40 H₂ O. (TPA₂)O=tetrapropylammonium hydroxide.

The reaction mixture for the preparation of the catalyst has thefollowing composition by mole (with the exclusion of Al₂ O₃ and B₂ O₃):0.05-0.15 (TAA)₂ O; 4-19 SiO₂ (of zeolite); 1 SiO₂ (of tetraalkylsilicate); 80-600 H₂ O.

A third object of the present invention is to provide a method for theselective decomposition of cumene hydroperoxide into phenol and acetoneusing the above catalyst.

The method according to the present invention consists in contactingcumene hydroperoxide with the catalyst, preferably placed inside areactor on one or more stationary or fluidized beds at a temperature offrom 20° to 120° C., preferably of 40°-60° C., and in discharging thereaction products and undecomposed cumene hydroperoxide. Cumenehydroperoxide can be supplied as such, or diluted in a suitable solventand, in particular, cumene.

The space speed LHSV referred to cumene hydroperoxide in the case ofcontinuous operating is between 0.5 and 10 h⁻¹. For the batchwiseoperation, the permanence time is within the range of from 1' to 120',preferably of 15 min.-20 min.

Some Examples having the purpose of better illustrating the inventionshall be now set forth. The specific examples are in no way intended tolimit the scope of the present invention.

EXAMPLE NO. 1

An amount of 67.8 g of Al(NO₃)₃.9H₂ O is dissolved in 1275 g of ethylalcohol and to these compounds, under stirring, 2819 g oftetraethyl-silicate is added, with stirring being continued until ahomogeneous and clear solution is obtained.

Into a stainless steel vessel 1036 g of deionized water, 8878 g of anaqueous solution at 15.5% by weight of tetrapropyl-ammonium (TPA⁺)hydroxide and 167.5 g of powder of boric acid are added sequentially andunder stirring. When the acid has been completely dissolved, to thissolution the previously obtained solution is added, and the mixture isstirred while being heated at 60° C. for about 4 hours and in any caseuntil the hydrolysis of the silicate is completed, and the present ethylalcohol has been nearly completely removed. The molar composition of thereaction mixture is the following:

SiO₂ /Al₂ O₃ =150; SiO₂ /B₂ O₃ =10; TPA⁺ /SiO₂ =0,5; H₂ O/SiO₂ =35.

The so-obtained solution is charged into an autoclave equipped with astirrer and is heated under its autogenous pressure under stirring for 4hours at 170° C. The discharged product is centrifuged and the cake isaccurately dispersed in 70 liters of deionized water, and the obtainedsuspension is again centrifuged, yielding a washed cake.

An amount of 2451 g of tetraethylsilicate is hydrolyzed in the presenceof 216 g of a solution at 15.5% of tetrapropyl-ammonium hydroxide and1300 g of deionized H₂ O. The washed cake discharged from the centrifugeis accurately dispersed into the so-obtained clear solution, until amilky suspension is obtained. Such suspension is fed to a spray dryerand atomized so as to obtain microspheres having an average diameterwithin the range of from 10 to 30 μm. The product is calcined for 1 hand 30 min. under N₂, with the temperature being raised from roomtemperature to 550° C., and then at a constant temperature of 550° C. inair for an additional 4 hours. The finished catalyst (A) is thusobtained, the chemical analysis of which is as follows:

SiO₂ : 96.87; Al₂ O₃ : 1.851; B₂ O₃ : 1.029; H₂ O; balance to 100.

To 50 g of a phenol/acetone (50% by mole) solution, kept at atemperature controlled at 40° C., 3 g of catalyst A and then 17 g ofcumene hydroperoxide are added. The decomposition is monitored byiodimetric titration and gas-chromatographic analysis.

The results are reported in Table 1.

EXAMPLE NO. 2

Following the procedure as disclosed in Example 1, the washed cakedischarged from the centrifuge is obtained. The solid is calcined underH₂ with the temperature being raised from room temperature to 550° C.and then at a constant temperature of 550° C. in air for 4 hours.

The product obtained (B) has the following chemical composition:

SiO₂ : 96.93; Al₂ O₃ : 1.968; B₂ O₃ : 0.852; H₂ O: balance to 100.

By the reactants and procedures as disclosed in Example 1, with theexception that 3 g of catalyst B is used in lieu of the 3 g of catalystA, the results described in Table 1 are obtained.

EXAMPLE NO. 3 (COMPARISON)

Into a 100-cc beaker, 1 g of Al(NO₃)₃.9H₂ O is dissolved in 18.8 g ofanhydrous C₂ H₅ OH and to the solution obtained, 41.6 g oftetraethyl-silicate is added.

Into another vessel of pyrex glass, 15.3 g of H₂ O, 131 g of aqueoussolution of tetrapropyl-ammonium hydroxide at 15.5% by weight and thepreviously prepared alcoholic solution are added under stirring. Thewhole solution is heated at 60° C. under stirring for about 4 hours, andin any case until the hydrolysis of the silicate has ended and ethylalcohol has been nearly completely removed. The solution obtained, whichhas the following molar composition: SiO₂ /Al₂ O₃ =150; TPA⁺ /SiO₂ =0,5;H₂ O/SiO₂ =35, is charged into an autoclave equipped with a stirrer andheated under stirring, under its autogenous pressure, at 170° C. for 4hours.

The discharged milky suspension is centrifuged, the cake is dispersed in500 g of deionized water and the suspension is centrifuged. The washedcake is then calcined by increasing the temperature, over 1 h and 30min. under N₂, from room temperature to 550° C. and then at a constanttemperature of 550° C. in air for 4 hours. The product obtained (C) hasthe following composition:

SiO₂ : 96.58; Al₂ O₃ : 1.077; H₂ O: balance to 100.

By the reactants and procedures as disclosed in Example 1, with theexception that 3 g of catalyst C is used in lieu of the 3 g of catalystA, the results described in Table 1 are obtained.

EXAMPLE NO. 4 (COMPARISON)

Into a 300-cc beaker of pyrex glass, 131 g of an aqueous solution oftetrapropyl-ammonium hydroxide at 15.5% by weight, 15.3 of deionized H₂O, and 2.5 g of H₃ BO₃ are added under stirring. The whole solution isstirred, with heating if necessary, until a clear solution is obtained,and then 41.6 g of tetraethyl-silicate is added, always under stirring.The stirring is continued for 4 hours while heating at 60° C., andanyway until the complete hydrolysis of the silicate has occurred, andto the nearly total removal of ethyl alcohol. The solution obtained,which has the following molar composition:

SiO₂ /B₂ O₃ =10; TPA⁺ /SiO₂ =0,5; H₂ O/SiO₂ =35, is charged into anautoclave equipped with a stirrer and heated under stirring, under itsautogenous pressure, at 170° C. for 4 hours.

The discharged milky suspension is centrifuged, the cake is dispersed in500 g of deionized water, and the suspension is centrifuged. The washedcake is then calcined by increasing the temperature, over 1 h and 30min., under N₂, from room temperature to 550° C. and then at a constanttemperature of 550° C. in air for 4 hours. The product obtained (D) hasthe following composition:

SiO₂ : 97.55; B₂ O₃ : 1.954; H₂ O: balance to 100.

By the reactants and procedures as disclosed in Example 1, with theexception that 3 g of catalyst D is used in lieu of the 3 g of catalystA, the results described in Table 1 are obtained.

EXAMPLE NO. 5

By the procedure and reactants as disclosed in Example 1, thedecomposition of cumene hydroperoxide (CHP) is carried out by using, inlieu of the 3 g of catalyst A, 0.2 g of catalyst E (sulphuric acid inaqueous solution at 96%) and adjusting the addition rate of CHP so thatthe addition takes place within a time of 10'; the temperature is alwayskept at 40° C. After a total time of 30 min. the reaction mixture isneutralized by sodium bicarbonate, and analyzed by iodimetric titrationand gas-chromatographic analysis.

The results are reported in Table 1.

                                      TABLE 1                                     __________________________________________________________________________    CATA-                                                                              REACTION                                                                             CHP   % SELECTIVITY                                                                           % SELECTIVITY                                     LYST TIME   % CONV.                                                                             PHENOL    ACETOPHENONE                                                                             OTHERS                                 __________________________________________________________________________    A    15 min.                                                                              100   96%       3%         1%                                     B    20 min.                                                                              100   96%       3%         1%                                     C    120 min.                                                                             80    85.5%     8%         6.5%                                   D    120 min.                                                                             40    80.5%     12.2%      7.8%                                   E    30 min.                                                                              100   95%       3%         2%                                     __________________________________________________________________________

An example of continuous synthesis of phenol and acetone is nowpresented.

A test is carried out by operating continuously by using equipmentconsisting of a glass reactor of 0.5 l in volume, equipped withmechanical stirring means, automatic level control, temperature controlsystem, inlet for the cumene hydroperoxide solution, outlet for theoutflowing stream, and equipped with a filtering candle to avoid loss ofthe catalyst.

To exemplify the purpose, a test carried out at 60° C., by feeding asolution of CHP (84%) in cumene at the flow rate of 0.1 l/h, with areactants volume in the reactor of 0,12 l, 7 g of catalyst A, isdescribed. The reaction is monitored by means of iodimetric titrationand gas-chromatographic analysis of samples drawn at regular timeintervals.

The conversion of cumene hydroperoxide, after 10 hours of operation, is90%, with the effluent having the following composition (% by weight),with the exclusion of cumene:

CHP, 10%

Phenol, 54.2%

Acetone, 33.3%

Acetophenone, 1.3%

Others, 1.0%

The yields referred to CHP are generally higher than 98%.

In regards to the catalyst, at the end of the test, it still has thesame initial characteristics, apart from a light brown color.

It can be totally reactivated either by washing at high temperature(100°-150° C.) with methanol or with another suitable solvent, or bycalcination at 550° C. in air.

When it is used again after these treatments, it displays a behavioridentical to that of a sample of a just prepared catalyst.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

We claim:
 1. A method for the selective decomposition of cumene hydroperoxide into phenol and acetone, which comprises contacting cumene hydroperoxide with a catalyst at a temperature of from 20° to 120° C., wherein said catalyst comprises oxide forms of silicon, aluminum, and boron constituting crystals having a structure of zeolite, wherein aluminum, and boron replace silicon in the crystalline structure of silica, and the crystals are interconnected with each other by oligomeric silica.
 2. The method according to claim 1, wherein cumene hydroperoxide is contacted with the catalyst at a temperature of from 40° to 60° C.
 3. The method according to claim 1, wherein the molar ratio of the silica of zeolite crystals to the oligomeric silica is within the range of from 80 to
 95. 4. The method according to claim 1, wherein said catalyst is in the form of microspheres having diameters within the range of from 5 to 1000 μm.
 5. A method for the selective decomposition of cumene hydroperoxide into phenol and acetone, which comprises (a) contacting cumene hydroperoxide with a catalyst placed in a reaction system at a temperature of from 20° to 120° C., wherein said catalyst comprises oxide forms of silicon, aluminum, and boron constituting crystals having a structure of zeolite, wherein aluminum and boron replace silica in the crystalline structure of silica, and the crystals are interconnected with each other by oligomeric silica; and (b) discharging phenol, acetone, and undecomposed cumene hydroperoxide from said reaction system.
 6. The method according to claim 5, wherein said reaction system is a reactor or a fluidized bed.
 7. The method according to claim 5, wherein cumene hydroperoxide is contacted with said catalyst at a temperature of from 40° to 60° C.
 8. The method according to claim 5, wherein said cumene hydroperoxide which is contacted with said catalyst is diluted in a solvent.
 9. The method according to claim 8, wherein said solvent is cumene.
 10. The method according to claim 5, which is conducted batchwise in a time of from 1 minute to 2 hours.
 11. The method according to claim 10, which is conducted batchwise in a time of from 15 minutes to 20 minutes.
 12. The method according to claim 5, which is conducted continuously at a space speed LHSV in reference to cumene hydroperoxide of between 0.5 and 10 h⁻¹. 